Findings of Thyroid Ultrasound Examination Within 3 Years After the Fukushima Nuclear Power Plant Accident

The Fukushima Health Management Survey

Hiroki Shimura; Tomotaka Sobue; Hideto Takahashi; Seiji Yasumura; Tetsuya Ohira; Akira Ohtsuru; Sanae Midorikawa; Satoru Suzuki; Toshihiko Fukushima; Shinichi Suzuki; Shunichi Yamashita; Hitoshi Ohto

Disclosures

J Clin Endocrinol Metab. 2018;103(3):861-869. 

In This Article

Abstract and Introduction

Abstract

Context: Childhood thyroid cancer is of great concern after the Fukushima nuclear power plant accident. Baseline analytical data on thyroid ultrasound examination (TUE) in children are important for future studies.

Objective: We analyzed the age and sex distribution of findings from the TUEs of children and adolescents in the Fukushima Health Management Survey (FHMS).

Design, Setting, and Participants: From October 2011 through March 2014, 294,905 participants aged 18 years or younger at the time of the earthquake voluntarily had TUEs in the first round of the FHMS. A secondary confirmatory examination was performed in 2032 subjects. Age- and sex-dependent prevalence and size of thyroid cysts, nodules, and cancers were analyzed.

Main Outcome Measures: Age, sex, and size distribution of findings were analyzed.

Results: Thyroid cysts, nodules, and cytologically suspected cancers were detected in 68,009, 1415, and 38 male subjects and in 73,014, 2455, and 74 female subjects, respectively. There was an age-dependent increase in the detection rate of thyroid nodules and cancer, but that of cysts reached a peak at 11 to 12 years. Sex affected the prevalence of thyroid nodules and cancers after the onset of puberty, but only a small difference was exhibited in that of cysts.

Conclusions: The thyroid cancer detection rate in Fukushima was clarified, and the proportion of individuals with thyroid nodules and cysts varied substantially by age. The results of this study will contribute to future epidemiological research on nodular thyroid diseases in children and adolescents.

Introduction

Childhood thyroid cancer is of great concern in Fukushima Prefecture, and the fear of cancer is prominent throughout Japan because previous studies have reported that one of the main adverse health effects of radiation fallout from nuclear power plant accidents, especially the Chernobyl nuclear power plant accident, has been a substantial rise in thyroid cancer among exposed young people.[1–3] Because radiation exposure levels in Fukushima residents were considered to be much lower than those in Chernobyl residents, a large increase in thyroid cancer rates due to radiation exposure, such as that which occurred after the Chernobyl accident, had not been expected.[4] However, it was necessary to conduct surveys for both scientific and social demands.[5] The Fukushima prefectural government started to examine thyroid glands by using ultrasound examination and common standardized diagnostic criteria among residents aged 18 years or younger from 7 months after the Fukushima Daiichi nuclear power plant accident[5–7] The first-round survey, during the first 3 years after the accident, is evaluated as baseline data prior to the period in which radiation effects on the thyroid gland could potentially occur.[5]

Because there have been no data on the thyroid ultrasound examination (TUE) among asymptomatic children and adolescents in a population of this size (i.e., hundreds of thousands),[8] it is worthwhile to share some of the findings from the survey. The same examination and diagnostic methods were used in a study of 3- to 18-year-old children performed in three prefectures located far from Fukushima (Aomori, Yamanashi, and Nagasaki), for a total sample size of 4365.[9–11] We report herein the precise age and sex differences in the findings from the TUEs performed on children and adolescents, which was conducted in the first-round examination of the Fukushima Health Management Survey (FHMS). The results demonstrated in this study will serve as reference data for future epidemiological studies of nodular thyroid diseases in children, adolescents, and young adults.

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